public class Round {

        private static final double π = 3.14;
        private double radius;

        public Round(double radius) {
            this.radius = radius;
        }

        public double area() {
            return π * radius * radius;
        }

        public static void main(String[] args) {
            Round round = new Round(10);
            System.out.println("圆的面积是：" + round.area());
        }
    }



